Prior art automatic plant watering apparatus has generally suffered from several deficiencies. One type of automatic plant watering apparatus is an elevated reservoir with a spring loaded valve therein which is actuated by the loss of weight of water by the plants in containers supported by the spring. One sigificant deficiency of this prior art apparatus in that the force which the spring brings to bear upon the valve increases as the room temperature increases. This causes the plants to be overwatered on hot days, beyond the increased amount of water needed to compensate for the higher evaporative rate. In addition, the prior art apparatus can service only a limited number of plant containers since all plant containers serviced must be mounted on the apparatus itself. Other prior art automatic plant watering apparatus suffer from the deficiences that they require complex mechanical mechanisms to operate, are bulky and unsightly in a domestic environment, and are generally expensive to fabricate and to operate.